I am glad that gpoquiz's simulation results essentially confirmed what I already wrote in this thread based on my own experience of playing about 1,000 games with AI namely that the win ratio is approximately 50:50 and that, on average, one game lasts 5-6 rounds.
It would be interesting if he tried to simulate the same number of games to see what the starting situation is for a player who goes first and, after the board is generated, has only cards with a value of 1 or 2 around them. For me, this worked out to be about 30% of the board generation. Here, the imaginary advantage of the first move turns against the player. And it's true that in the case of playing with AI, I've noticed this many times, whether on the player's side or the AI's.
As for Shift mode, I am convinced that it will not be possible to combine it with Solo mode. Solo mode must have a generated solvable board, where the algorithm has clearly defined information about the game board, including coordinates, and assembles the game board in reverse (classic solo mode 3x3 or 4x4). In combination with Shift mode, the size of the board is known at the beginning of the game, but no one knows what the game board will look like at the end of the game. But maybe I'm wrong and someone will build a generator for Shift mode that will generate at least one path for solo mode with cards moving one space in a row or column after each move.